Fluid sensing gauges are used in many applications. A common type of gauge is the float gauge, which mounts a float which floats atop the surface of the fluid being measured. The float is connected to a pivot arm or member which moves with the float as the fluid level changes. Movement of the arm is sensed by a gauge, typically through a magnetic coupling, to provide an indication, either visual or otherwise, of the fluid level.
A common float gauge used for many years incorporates a variable resistor in the gauge to vary a resistance with a change in the fluid level. In such a gauge, a wiper arm is moved along a resistance element as the float changes level. The resistance is measured between one end of the resistance element and the wiper arm, which corresponds to the float position. While such a circuit is effective, it does suffer certain disadvantages. These disadvantages include the requirement for adjusting the resistance output to correspond to the float position. Further, change in such variables as contact resistance, hook-up wire length, temperature, and voltage applied across the resistance can actually vary the response of the gauge, leading an inability to reproduce results and maintain gauge accuracy.
A need therefore exists for an improvement in the basic float gauge apparatus which overcomes the deficiencies of the variable resistor gauge.